Flow control valve

ABSTRACT

A fluid circuit includes a flow control valve comprising surge damping and counterbalance pressure control valves for controlling the actuation of a cylinder having the rod thereof operatively connected to an implement, such as a loader bucket lift arm. The counterbalance pressure control valve maintains a sufficiently high back pressure in the cylinder during the &#39;&#39;&#39;&#39;hold&#39;&#39;&#39;&#39; phase of loader operation to prevent the loader bucket from creeping downwardly. The surge damping valve co-operates with the latter valve to freely communicate pressurized fluid to the cylinder during the &#39;&#39;&#39;&#39;raise&#39;&#39;&#39;&#39; phase of loader operation and to automatically regulate return flow during the &#39;&#39;&#39;&#39;lower&#39;&#39;&#39;&#39; phase in direct proportion to the magnitude of load imposed on the cylinder rod by the loader bucket.

United States Patent 1191 Cryder 51 Apr. 24, 1973 1 1 FLOW CONTROL VALVE3,015.341 1/1962 Hedland et a1. ..137 504 x Inventor: J R. y Joliet, 1"3,120,243 2/1964 Allen et a1. ..137/504 [73] Assignee: CaterpillarTractor Co., Peoria, 111. Primary ExaminerEdgar W. Geoghegan AssistantExarr1inerlrwin C. Cohen [22] Filed: 1970 Att0rney-Fryer, Tjensvold,Feix, Phillips and Lempio 21 App1.No.: 92,192

[57] ABSTRACT Related US. Application Data A fluid circuit includes aflow control valve compris- Continuation of 56f. NO. 768,733, OCL 18,1968, ing urge damping and counterbalance pressure con. abandonedtrolvalves for controlling the actuation of a cylinder having the rodthereof operatively connected to an im- [52] US. Cl .,.....9l/447,137/504 plement, Such as a loader bucket lift arm The coun 51 1111.01...F15b 11/08, F15b 13/04 terbalance pressure Control valve maintains a[58] Field of Search ..91/437, 443, 447, ciemly high back pressure inthe Cylinder during the 91/468, 445 448; 137/504 hold phase of loaderoperation to prevent the loader bucket from creeping downwardly. Thesurge damping References Cited valve co-operates with the latter valveto freely communicate pressurized fluid to the cylinder during the 1UNITED STATES PATENTS raisel phase of loader operation and toautomatically 2,618,121 11/1952 Tucker ..91/447 X regulate return flowduring the lower phase in 2,991,759 7/1961 Pilchm ....91/447 X directproportion to the magnitude of load imposed on 3,072,107 1/1963 Cassell.1 ,...9l/447 X the cylinder rod by the loader bucket. 3,127,688 4/1964Hein et a1. ....91/437 X 3,438,308 4/1969 Nutter ..91/447 X 7 Claims, 2Drawing Figures mzmms 3,728,941

' SHEEIIOFZ I INVENTORS JOHN R. CRYDER ATTORNEYS PAIENTEDAPR 24 I975SHEET 2 OF 2 INVENTORS BY I W W,

m m w E R m c T T R TA N O m 0/ FLOW CONTROL VALVE This application is aContinuation of application Ser. No. 768,733, filed Oct. 18, 1968, andnow abandoned.

Double-acting hydraulic cylinders, such as those used for lowering andraising the lift arms of loader buckets, are subjected to heavy andvarying loads during earth-moving operations. The increased size andcapacity of present day loaders dictate the need for high capacity pumpsfor actuating the loaders lift and tilt circuits efficiently andexpeditiously. For example, maximum system pressure limits for largeloaders have been increased above presently used pressure levels. Suchhigher pressure levels render conventional circuits prone to leakage andrelated problems requiring design changes thereto, such as the closingof control valve tolerances.

An object of this invention is to provide a fluid circuit, particularlyuseful for high pressure applications, having a non-complex flow controlmeans for efficiently controlling the operation of an actuating means,such as a The cylinder. The flow control means preferably comprisessurge damping means for automatically restricting the rate of returnfluid flow from the cylinder to a pressurized fluid source in directproportion to the increase in the fluid pressure level prevalent in anexpansible chamber of the cylinder resulting from an increased loadingofa rod thereof.

The preferred flow control means embodiment functions to permit the rodto retract at a substantially constant linear velocity regardless of themagnitude of load imposed thereon. Another feature of this inventioncomprises counterbalance control means employed in the flow controlmeans to aid in maintaining the desired back pressure in the cylinderduring a hold or neutral condition of operation thereof.

Further objects of this invention will become apparent from thefollowing description and accompanying drawings wherein:

FIG. 1 schematically illustrates a fluid circuit, employing the flowcontrol means of this invention therein, in its neutral or holdcondition of operation; and

FIG. 2 is a view identical to FIG. 1, except that the fluid circuit isshown in a lower or cylinder retraction condition of operation.

The fluid circuit illustrated in FIG. 1 comprises an engine-driven pumpco-operating with a fluid retaining reservoir 11 to provide apressurized fluid source. The source preferably communicates pressurizedoil or other suitable fluid to a selector control valve 12 via branchconduit 13. Conventional pressure relief valve 14 may be set to relievesystem pressures exceeding 5,000 to 6,000 p.s.i., if necessary. itshould be noted that such pressure level substantially exceeds maximumpressure levels normally prevalent in fluid circuits of the type hereindescribed.

The selector control valve is illustrated in its neutral or hold Hposition (FIG. 1) whereby conduit 13 communicates with a return conduit15 to vent pressurized fluid back to the reservoir. Spring means 16 maybe employed in a conventional manner to normally return the valves spoolto such neutral position upon release thereof by the operator.Subsequent movement of the valve to its raise R or lower L position willfunction to operate an actuating means, preferably a double-actingcylinder 17, mechanically connected to an implement means such as theillustrated loader bucket B.

Although the fluid circuit is hereinafter described as functioning toraise or lower the lift arms (not shown) of a loader, it should beunderstood that this invention contemplates a wide variety of otherapplications therefor. In addition, the actuating means could constituteother well-known fluid actuated devices. Also, the implement means couldcomprise conventional loader bucket tilt linkages, a bulldozer blade, amoveable element of a hydraulically actuated machine tool or othersuitable devices.

When the selector control valves spool is manually shifted to its raiseR position, conduit 13 communicates with a conduit 18 to supplypressurized fluid to a flow control valve or means 19. The latterconduit communicates with an inlet passage means comprising an annularchamber 20 formed in the valves housing. The chamber, in turn, normallycommunicates with variable port means, preferably in the form of radialports 21, formed in a spool 22 reciprocably mounted in the housing. Thespool further comprises a flange or baffle means 23 and chamber 24formed internally thereof for purposes hereinafter described.

A coil spring 25 is disposed between an end plate of the housing and thespool to normally urge the spool in a rightward or first directionagainst a maximum stop means or shoulder 26 of the two-part housing.When fluid pressure in chamber 24 exceeds a predetermined level acup-shaped piston 27 will move rightwardly from its normal blockingposition against the opposing force of a coil spring 28. Substantiallyunrestricted fluid flow will then pass by the illustrated valve seat andinto an outlet passage means comprising an annular chamber 29 andconduit 30 to pressurize an expansible chamber at the head end ofcylinder 17. Such pressurization will function to move a rod 31 of thecylinder rightwardly to raise loader bucket B for earth-moving orunloading purposes.

During the raising phase of loader operation the rod end of the cylinderwill be maintained in vented communication with the reservoir by meansof conduit 32. In addition, a conduit 33 communicates with a chamber 34formed in part by piston 27 to exhaust fluid pressure in such chamber.Thus, the force of the pressurized fluid in chamber 24 need onlyovercome the counteracting force of spring 28 to supply such fluid tothe cylinder. It should be further noted that the piston has at leastone orifice 35 formed therein to normally communicate chambers 29 and 34for the purposes hereinafterdescribed.

When bucket B has been raised to its desired, elevated position, theoperator will release the selector control valve's spool toautomatically place the circuit in its normal FIG. 1 hold H condition.The loader bucket is prevented from creeping downwardly primarily due tocounterbalancing pressure control means comprising piston 27. Inparticular, a leftwardly directed force imposed on rod 31 willproportionately increase the fluid pressure level in the expansiblechamber at the head end of the cylinder and in conduit 30. Such increasewill be communicated to chamber 29, through orifice 35 and into chamber34. Since venting via conduits l8 and 33 is now blocked by the selectorcontrol valve, the force of spring 28 and the increased fluid pressurein chamber 34 will hold piston 27 against its seat to prevent fluidleakage thereby to chamber 24.

When the selector control valve is shifted to its lower L position (FIG.2), pressurized fluid communicates throughconduits l3 and 32 to the rodend of the cylinder. Fluid expelled from the head end thereof flows fromconduit 30 and into annular chamber 29 to urge piston 27 rightwardly.Such rightward movement is caused by the fluid pressure acting on anannular surface area 36 formed externally on piston 27 which overcomesthe counteracting biasing force of spring 28. Surface area 36 may beconsidered as a differential surface area means, relative to the reducedsurface area at the left end of the piston, continuously exposed tofluid pressure in conduit 30. It should be noted that during loweringphase of loader operation that conduit 33 functions to exhaust chamber34.

Another feature of this invention is the provision of surge dampingmeans for automatically decreasing the return fluid flow rate from theexpansible chamber of the cylinder in direct proportion to an increasein the fluid pressure level prevalent therein. Such increased pressurelevel will, of course, be directly proportional to the magnitude of loadimposed on rod 31 to move it leftwardly. Such means comprises bafflemeans 23, formed internally of spool 22, arranged to have the returningfluid impinge thereon to urge the spool in a second, leftward direction.The flow rate of the returning fluid dictates the magnitude of forceurging the spool leftwardly and is proportional to the abovementionedload imposed on rod 31.

Leftward movement of the spool will function to at least partially closevariable port means 21, as illustrated in FIG. 2, to reduce the flowrate of returned fluid to exhaust conduits l8 and 15. Thus, it can beseen that such surge damping means will function in the preferredembodiment to maintain a substantially constant retraction or linearspeed of rod 31 regardless of the magnitude of the load imposed thereonby the bucket. For example, when bucket B is empty to thus impose aminimal force on the rod the velocity of fluid flow in chamber 24 issufficiently and proportionately low to not move spool 22 leftwardly.Thus, the fluid will freely flow through fully exposed ports 23 to lowerthe bucket at the predetermined, constant rate.

However, when a loaded bucket is lowered, for example, a considerablygreater force is imposed on rod 31 to accelerate fluid flow in chamber22 to a substantially higher velocity. Such increased fluid flow willimpinge against baffle means 23 to move spool 22 leftwardly in directproportion to the load imposed on rod 31 and the increased pressurelevel prevalent in the expansible chamber at the head end of thecylinder. Thus, ports 21, which are suitably calibrated, function to atleast partially close and restrict return fluid flow into conduit 18. Adesired and constant back pressure is thus automatically created at thehead end of the cylinder to maintain the retraction speed of thecylinder rod substantially constant.

Likewise, when sudden pressure surges are created in the system bycatching a descending and loaded bucket, for example, such surges willnot become excessive since spool 24 will move leftwardly in a likemanner to automatically regulate fluid outflow to conduit 18. Whenreturn flow is terminated by shifting selector control valve 12 to itsFIG. 1 hold H position, spool 27 will seat immediately under theinfluence of spring 28 to prevent undue pressurization in conduit 18 andvalve 12.

I claim:

1. In a fluid circuit comprising:

. a pressurized fluid source,

b. actuating means including a fluid pressure load responsive expansiblechamber,

c. selector control valve means operatively connectable to said source,and

d. expansible chamber flow control means operatively connected to saidvalve means and said chamber including:

1. surge damping means including a housing containing a first annularchamber, a spool positioned in said housing, a single set of radialports in said spool communicating fluid between said valve means, saidfirst annular chamber, and a first interior chamber of said spool,spring means positioning said spool in said housing in normally opencommunication through said ports, axial port means in said spoolcommunicating normally unrestricted fluid flow between said first spoolinterior chamber and a second spool interior chamber, and surge dampingflow restricting baffle means formed on said spool and defining saidaxial port and between said first and second spool chambers, said surgedamping means automatically decreasing the flow rate of fluid returnedfrom said actuating means to said pressurized fluid source through saidvalve means in direct proportion to an increase in the magnitude ofloads imposed on said actuating means and a resulting increase in thefluid pressure level present in the expansible chamber thereof, andprovides substantially constant speed of the motion of said actuatingmeans, and

2. counterbalance pressure control means between said second spoolchamber and said actuating means including a piston positioned in achamber formed by a counterbalance housing, a second annular chamberformed by said piston and said counterbalance housing, and fluid backpressure maintaining spring means between said piston and saidcounterbalance housing, said counterbalance means maintaining said fluidback pressure in the chamber of said actuating means when fluid flowfrom said pressurized fluid source to said actuating means is prevented.

2. The invention of claim 1 wherein said actuating means comprises adouble-acting cylinder having a rod reciprocally mounted therein.

3. The invention of claim 2 further comprising implement meansoperatively connected to the rod of said cylinder for varying the fluidpressure level in said expansible chamber in direct proportion to theload imposed on said rod by said implement means.

4. The invention of claim 3 wherein said implement means comprises aloader bucket adapted to be raised and lowered by said cylinder.

5. The invention of claim 1 wherein said flow control means furthercomprises stop means for setting maximum movement of said spool in thedirection urged by said spool spring means.

6. The invention of claim 1 wherein said piston further includes aradial surface positioned in said second annular chamber formedexternally thereon and continuously exposed to fluid pressure in theexpansible chamber of said actuating means for urging said piston to anopen position against the biasing force of said fluid back pressuremaintaining spring means.

7. The invention of claim 6 wherein said piston forms a chamber in saidcounterbalance pressure control

1. In a fluid circuit comprising: a. a pressurized fluid source, b.actuating means including a fluid pressure load responsive expansiblechamber, c. selector control valve means operatively connectable to saidsource, and d. expansible chamber flow control means operativelyconnected to said valve means and said chamber including:
 1. surgedamping means including a housing containing a first annular chamber, aspool positioned in said housing, a single set of radial ports in saidspool communicating fluid between said valve means, said first annularchamber, and a first interior chamber of said spool, spring meanspositioning said spool in said housing in normally open communicationthrough said ports, axial port means in said spool communicatingnormally unrestricted fluid flow between said first spool interiorchamber and a second spool interior chamber, and surge damping flowrestricting baffle means formed on said spool and defining said axialport and between said first and second spool chambers, said surgedamping means automatically decreasing the flow rate of fluid returnedfrom said actuating means to said pressurized fluid source through saidvalve means in direct proportion to an increase in the magnitude ofloads imposed on said actuating means and a resulting increase in thefluid pressure level present in the expansible chamber thereof, andprovides substantially constant speed of the motion of said actuatingmeans, and
 2. counterbalance pressure control means between said secondspool chamber and said actuating means including a piston positioned ina chamber formed by a counterbalance housing, a second annular chamberformed by said piston and said counterbalance housing, and fluid backpressure maintaining spring means between said piston and saidcounterbalance housing, said counterbalance means maintaining said fluidback pressure in the chamber of said actuating means when fluid flowfrom said pressurized fluid source to said actuating means is prevented.2. counterbalance pressure control means between said second spoolchamber and said actuating means including a piston positioned in achamber formed by a counterbalance housing, a second annular chamberformed by said piston and said counterbalance housing, and fluid backpressure maintaining spring means between said piston and saidcounterbalance housing, said counterbalance means maintaining said fluidback pressure in the chamber of said actuating means when fluid flowfrom said pressurized fluid source to said actuating means is prevented.2. The invention of claim 1 wherein said actuating means comprises adouble-acting cylinder having a rod reciprocally mounted therein.
 3. Theinvention of claim 2 further comprising implement means operativelyconnected to the rod of said cylinder for varying the fluid pressurelevel in said expansible chamber in direct proportion to the loadimposed on said rod by said implement means.
 4. The invention of claim 3wherein said implement means comprises a loader bucket adapted to beraised and lowered by said cylinder.
 5. The invention of claim 1 whereinsaid flow control means further comprises stop means for setting maximummovement of said spool in the direction urged by said spool springmeans.
 6. The invention of claim 1 wherein said piston further includesa radial surface positioned in said second annular chamber formedexternally thereon and continuously exposed to fluid pressure in theexpansible chamber of said actuating means for urging said piston to anopen position against the biasing force of said fluid back pressuremaintaining spring means.
 7. The invention of claim 6 wherein saidpiston forms a chamber in said counterbalance pressure control means andhas port means formed therethrough to communicate fluid between thechamber of said actuating means and the chamber of said piston and meansincluding said selector control valve means for selectivelycommunicating fluid from said counterbalance pressure control pistonchamber to said pressurized fluid source.